432 OP FOOD, AND THE DIGESTIVE PROCESS. 



many more hours are required. Thus a Cat, two hours after a full meal of flesh, 

 secreted at the rate of 7.5 grains of bile per hour; at the 4th hour, 9.7 grains; 

 at the 6th hour, 11.6 grains; at the 8th hour, 12.7 grains; and at the 10th 

 hour, 13 grains. From the 10th to the 24th hour, the secretion diminished at 

 the rate of 4.10ths of a grain per hour, until it reached the lowest of the above 

 amounts. The secretion is considerably diminished when food is withheld for 

 some time ; the quantity poured out after ten days' starvation being only about 

 one-eighth of what it is when at its maximum. Still it is obvious that, although 

 its rate is thus greatly influenced by the stage of the digestive process (which is 

 the less to be wondered at, when it is remembered that the secretion is formed 

 from blood that is charged with newly-absorbed and imperfectly assimilated 

 matters), the excrementitious character of the secretion requires that its elimi- 

 nation shall be constantly going on to a certain degree ; but a receptacle is pro- 

 vided in Man, as in most others among the higher animals whose digestion is 

 performed at intervals, for the storing-up of the fluid until it can be usefully 

 employed in that process. The intestinal orifice of the ductus choledochus is 

 closed by a sort of sphincter ; and the fluid secreted during the intervals of 

 digestion, not being propelled with a force sufficient to dilate this, flows back into 

 the gall-bladder, which dilates to receive it. The presence of food in the duo- 

 denum seems to excite the walls of the gall-bladder and of the biliary ducts 

 (which contain a large quantity of smooth muscular fibre, 305) to a contrac- 

 tion sufficiently powerful to propel their contents into the intestine, in spite of 

 the opposition of the sphincter ; but whether this takes place through a reflex 

 action of the nervous system, or through the direct stimulation of the muscular 

 coat of the duct by the passage of alimentary matters over its orifice, we have 

 at present no means of satisfactorily determining. It will be recollected that 

 the gall-bladder is usually found distended with bile, in cases of death from 

 starvation ( 417), notwithstanding the diminution in the amount actually 

 secreted. 



455. The fluid of the Small Intestines, which is compounded by the inter- 

 mixture of the biliary and pancreatic secretions, with the salivary and gastric 

 fluids, and with the secretion of the intestinal glandulae, appears to possess the 

 very peculiar power of dissolving or of reducing to an absorbable condition, 

 alimentary substances of every class ; thus possessing more of the character of 

 a "universal solvent/' than either of these secretions has in its separate state. 

 It completes the conversion of starchy into saccharine matter ; and thus enables 

 the former to supply the blood with an important pabulum for the combustive 

 process, which is at once absorbed into the bloodvessels. It emulsifies the 

 oleaginous matter, and thus renders it capable of being introduced into the 

 lacteals. And it not only restores to the state of solution the albuminous com- 

 pounds, which may have been precipitated by the addition of bile to the product 

 of gastric digestion; but it also exerts a powerful solvent influence upon albu- 

 minous substances which have not been submitted to the previous agency of 

 the gastric fluid (as has been shown by experimentally introducing pieces of 

 meat, through a fistulous orifice, directly into the duodenum), and it thus com- 

 pletes the solvent process which had been very far from perfected in the sto- 

 mach. 1 What is the precise share, however, of each of these secretions in 

 producing this composite result, cannot be stated with any degree of certainty; 

 but it seems probable that the secretions of the intestinal walls have a very 

 definite share in it. It is obvious that the amount of each kind of alimentary 

 substance that can be thus prepared for absorption in a given time, will vary 



.- 



1 See the account of M. Cl. Bernard's researches in the "Amer. Journ. of Med. Sci.," 

 Oct. 1851, p. 356; Zander, "De Succo Enterico," inaug. diss., Dorpat, 1850; Frerichs, 

 Art. Verdauung, in "Wagner's Handworterbuch;" and Liebig's " Annalen der Chemie," &c. 



